Temporal patterns of migratory shorebird communities at a stop-over site along the East Asian–Australasian Flyway

Migratory birds face serious time constraints in their life cycles. Species carry on their activities during optimal time windows to maximise their fitness. To understand the temporal patterns of migrating shorebirds, we analysed the pattern of turnover within shorebird communities during northward and southward migration at Chongming Dongtan, a stop-over site in the southern Yellow Sea along the East Asian-Australasian Flyway. Results indicated that temporal patterns in shorebird communities differed between seasons. In the boreal spring, the rate of community turnover was initially slow, then increased rapidly midseason, and finally stabilised. In the boreal autumn, in contrast, the rate of community turnover kept constant. This suggests that shorebird species exhibited more temporal overlap in spring than in autumn, perhaps because time constraints are more severe at breeding than non-breeding grounds. The species sequence was strongly linked with breeding latitude: species that breed farther north occurred at the study site later than those that breed farther south on both northward and southward migration. Moreover, large species were more likely to arrive at the stop-over site early on northward (but not on southward) migration than small species. Integrated with the results from intraspecific studies, we propose that the timing of migration is closely related to the breeding latitude both among and within species.